This invention relates to a catheter introducer well-suited for introducing a catheter into a blood vessel.
2. Description of the Prior Art
The conventional catheter introducer includes a sheath having a hollow structure extending continuously from a base end portion to a distal end portion, and a hub having a hollow structure and covered by the base end portion of the sheath. The introducer is used to introduce a catheter into a blood vessel. This is performed first by piercing a blood vessel such as an artery or vein with a Seldinger needle. Next, a guide wire is inserted into the blood vessel by being passed through the Seldinger needle. This is followed by withdrawing the Seldinger needle, leaving the inserted guide wire in place. Next, with a dilater inserted and set, the introducer is inserted into the blood vessel so as to pass over and cover the guide wire. The guide wire and dilater are then withdrawn, leaving the introducer in the blood vessel. A catheter may now be introduced into and withdrawn from the blood vessel by being passed through the introducer residing in the blood vessel. Alternatively, a transfusion line may be connected to the introducer to infuse the patient with a medical or other fluid.
The conventional catheter introducer has a number of disadvantages. Specifically, in a case where a patient is to be continuously infused with a medical or other fluid in a state where the catheter introducer is left in place for an extended period of time (e.g., one week), movements by the patient can cause the sheath to bend into a fold at the junction between the comparatively rigid hub and the sheath, which is comparatively flexible. In actual practice, there are many cases where sustained infusion of medical fluid cannot be carried out satisfactorily due to such bending. In order to prevent such bending of the sheath, a catheter introducer has been developed in which a tube is fitted over the junction between the hub and sheath. While a rigid tube can prevent the sheath from bending into a fold at the hub-sheath junction, the sheath loses overall flexibility, thus subjecting the patient to greater discomfort. If a flexible tube is adopted, on the other hand, the tube exhibits almost no effectiveness in terms of preventing bending of the sheath. A recent catheter introducer includes a sheath a section of which has a bellows-like configuration at the hub-sheath junction to prevent the sheath from bending into a fold. However, since the inner surface of the sheath at the bellows section has a number of indentations rather than being smooth, blood tends to reside in the indentations. This raises the possibility that thrombus will occur.
Another problem with the conventional catheter introducer is leakage of blood when the catheter is inserted into and withdrawn through the introducer left in the blood vessel. Accordingly, there is a requirement for a catheter introducer that is capable of reliably preventing leakage of blood at such times.